Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS64 KMRX 222024
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
324 PM EST MON DEC 22 2014

.SHORT TERM (TODAY THROUGH WEDNESDAY)...INCREASING LOW-LEVEL JET
ACROSS THE TENNESSEE VALLEY IN RESPONSE TO AN UPPER WAVE MOVING
ACROSS THE AREA WILL ENHANCE THE ISENTROPIC LIFT. INCREASING
DYNAMICS IS ALREADY INCREASING CONVECTION OVER THE PLATEAU AND
ALABAMA. FORECAST SOUNDING SHOWS ELEVATED INSTABILITY...SO HAVE
INCLUDED THUNDERSTORMS FOR THE SOUTHERN HALF OF THE AREA.

PLENTY OF LOW-LEVEL MOISTURE PULLING INTO THE SOUTHERN VALLEY WILL
ALSO PRODUCE EXTENSIVE FOG AND DRIZZLE OVERNIGHT ACROSS THE CHA
AREA.

FOR TUESDAY...DOWNSLOPING WINDS WILL HELP CLEAR OUT THE CLOUDS OVER
THE NORTHERN HALF OF THE VALLEY WHILE THE SOUTHERN HALF STAYS
WITHIN LOW-CLOUDS AND MORNING FOG/DRIZZLE.

A STRONG JET OVER THE OHIO VALLEY AND JET ASSOCIATED WITH INCOMING
UPPER TROUGH WILL PRODUCE STRONG UPPER DIVERGENCE OVER THE AREA
LATE TUESDAY AND TUESDAY NIGHT. AGAIN...GIVEN ELEVATED INSTABILITY
EXPECTED WIDE SPREAD SHOWERS AND CHANCE OF THUNDERSTORMS. SOME OF
THE RAIN COULD BE HEAVY OVER THE AREA...ESPECIALLY PLATEAU AND
SOUTHEAST TENNESSEE FOR TUESDAY NIGHT.

FOR WEDNESDAY...COLD FRONT MOVES THROUGH THE AREA PRODUCING
WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS. CONVECTION WILL END
FROM WEST TO EAST AS FRONTAL BOUNDARY MOVES ACROSS THE REGION.

.LONG TERM (WEDNESDAY NIGHT THROUGH MONDAY)...A BRIEF SHOT AT LIGHT
SNOW STILL POSSIBLE LATE CHRISTMAS EVE INTO EARLY CHRISTMAS MORNING.
NO ACCUMULATION EXPECTED EXCEPT FOR MAYBE UP TO AN INCH OR SO ACROSS
THE HIGHEST ELEVATIONS. THEN A WEEKEND SYSTEM APPROACHES THAT THE
MODELS STILL AREN`T HANDLING WELL.

BY WEDNESDAY EVENING THE BULK OF THE PRECIPITATION WILL HAVE PASSED
TO OUR EAST AS WE AWAIT THE PASSAGE OF THE COLD FRONT. THE GFS AND
THE NAM BOTH SHOW A DRY SLOT BETWEEN THE FRONTAL PASSAGE AND THE
FINAL PUSH OF PRECIP INTO THE AREA. THIS MEANS THERE WILL LIKELY BE
A BREAK BETWEEN THE LIQUID PRECIP AND ANY SNOW THAT OCCURS. THE WRAP
AROUND MOISTURE AND ASSOCIATED SHORTWAVE COMES IN CLOSE TO MIDNIGHT.
AS OF NOW...IT LOOKS LIKE LOCATIONS NORTH OF 1-40 MAY BE THE ONLY
ONES TO SEE ANY SNOW. THE LOWER ELEVATIONS ACROSS THE SOUTHERN
VALLEY APPEAR TO BE TOO WARM FROM THE LATEST GUIDANCE. AREAS NORTH
OF I-40 MAY SEE LIGHT SCATTERED SNOW SHOWERS/FLURRIES AFTER MIDNIGHT
AND INTO EARLY CHRISTMAS MORNING...THE BEST CHANCES WILL BE ACROSS
NETN AND SWVA. PRECIP QUICKLY MOVES OFF TO THE NORTHEAST DURING THE
MID TO LATE MORNING HOURS OF CHRISTMAS DAY AND SOME AREAS MAY EVEN
SEE A CHANGE OVER BACK TO LIGHT RAIN/DRIZZLE BEFORE THE PRECIP
COMPLETELY EXITS. AS THE DAY PROGRESSES THE CLOUDS SHOULD ERODE FROM
SW TO NE...BRINING SUNSHINE TO MOST AREAS BY MID TO LATE AFTERNOON.
WE SHOULD STAY DRY FROM THURSDAY EVENING THROUGH MOST OF THE DAY
FRIDAY WITH SUNSHINE BRIEFLY RETURNING.

BRING PRECIP BACK IN FRIDAY NIGHT AND KEEP IT INTO MONDAY. MODELS
STILL DOING A VERY POOR JOB HANDLING THIS NEXT SYSTEM. THE ECMW
LOOKS WET WITH A POTENT SHORTWAVE SWINGING THROUGH WHILE THE GFS IS
MUCH DRIER WITH NOTHING MORE THAN A WEAK FRONT CRUISING THROUGH.
WILL GO WITH A BLEND OF POPS BETWEEN THE GFS AND ECMW UNTIL THEY
BETTER AGREE. DURING THIS TIME FRAME...IT MAY BE COLD ENOUGH TO SEE
SOME LIGHT SNOW ACROSS ACROSS THE HIGHER TERRAIN.

&&

.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN             45  55  53  62 /  70  90 100  90
KNOXVILLE MCGHEE TYSON AIRPORT, TN  43  61  50  65 /  60  80 100 100
OAK RIDGE, TN                       43  58  52  63 /  60  80 100  90
TRI CITIES AIRPORT, TN              37  60  48  65 /  50  50  80 100

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.